The present invention relates to a method of producing a gas barrier layer using plasma-enhanced CVD, and more specifically to a gas barrier layer production method capable of forming a gas barrier layer having excellent gas barrier properties and oxidation resistance, as well as a gas barrier film for solar batteries and a gas barrier film for displays which use the gas barrier layer production method.
A gas barrier layer (a water-vapor barrier layer) is formed not only on sites or parts requiring moisture resistance in various devices including optical devices, display devices (e.g. liquid-crystal displays and organic EL displays), semiconductor devices and thin-film solar batteries, but also in packaging materials used to package food, clothing, electronic components, etc. A gas barrier film having a gas barrier layer formed on a plastic film substrate made of, for example, PET is used in various applications including the foregoing applications.
Layers made of various substances such as silicon oxide, silicon oxynitride and aluminum oxide are known gas barrier layers. A gas barrier layer made of silicon nitride is known as one of those layers. Plasma-enhanced CVD is a known method of producing a gas barrier layer made of silicon nitride.
For example, JP 2008-214677 A describes a gas barrier layer production method in which a gas barrier layer made of silicon nitride is formed on a substrate surface by plasma-enhanced CVD using silane gas, ammonia gas and a carrier gas, wherein two or more silicon nitride sublayers having different Si/N composition ratios are deposited by maintaining the substrate temperature at 200° C. or less and adjusting the flow rate ratio of the ammonia gas to the silane gas.
This production method is capable of obtaining a gas barrier layer which exhibits high oxidation resistance in a high temperature and high humidity environment, has few pinholes and exhibits high transparency (optical transmittance).